IEC 62304 is the standard to apply for software in medical devices. It is not bound to any software development method or model. Though not explicit, using the waterfall development model is the most straighforward way to apply this standard.
The waterfall model has become old fashioned to the eyes of most of software developers, with the emergence of agile methods. Agile methods are so popular now that everydody wonders how to apply IEC 62304 with agile methods.

Congratulations! You have signed a contract with a medical devices manufacturer. They don't have a very good knowledge of software. They rely on you to develop something brand new on a smartphone. The application they want to develop will bring new functionalities to doctors and let them do their jobs faster. Your customer chose you because you are the specialist of software on every OS’es on smartphones. You ensured him that your company can be in conformity with IEC 62304 standard. To that purpose, you modified and added the necessary procedures and forms to your quality system.
You have one year to develop the application, which fits their desires … and the medical devices standards!

Case example

You are a medical device company and you want to replace your old products by “smart” ones. Your competitors are doing it and you customers want them. “Smart” means something like an tiny computer (its amazing how small they are), with an operating system and big software. For electronic stuff, you have your own engineers or you have your subcontractors, which you have been working for 20 years with. They knew how to design embedded software on microchips. But they don’t know how to design software of higher level, with intelligent behaviour and complex algorithms.